1. Field of the Invention
The present invention relates to medical devices and other similar devices and in particular to medical devices such as intravenous catheters and syringes which include a hollow needle having a sharp distal end for piercing an object, such as the skin of a patient.
2. Background of the Invention
The existence of infectious diseases has highlighted the danger to which medical personnel may be exposed when treating patients by means of catheter devices and syringes where a sharp needle point is used to pierce the skin of the patient. In order to protect medical personnel against inadvertent needle stick, a number of solutions have been developed whereby a protective mechanism, incorporated within a catheter or syringe, prevents physical contact with the sharp needle point after use and hence protects against inadvertent needle stick. Many of the developed solutions are complicated. For example, some developments utilize the retraction of the needle within a housing once the needle has been used. Other developments utilize blunts which are contained within the cannula of the hollow needle.
These blunts come in two principal forms: hollow blunts which are hollow tubes concentrically disposed within the circular shaft of a hollow needle, and solid blunts. Hollow blunt designs require that an exit hole be provided at a proximal location to allow blood to exit the blunt and enter a flash chamber, the use of which is well known in the art. In order for blood flashback to be seen as quickly as possible, the exit hole needs to be located just proximal to the butt end of the needle. Thus, hollow blunts require extra machining or manufacturing steps in order to produce a satisfactory hollow blunt. Solid rod blunts are typically cylindrical rods which have an outer diameter which is sufficiently smaller than the inner diameter of the shaft of the cannula of the needle in order to allow clearance for fluid flow all around the diameter of the solid rod blunt. While some prior art designs have included grooves in the solid rod blunt, these solid rod blunts nevertheless position the wall of the blunt (the outside diameter of the blunt) some distance from the inner diameter of the shaft of the cannula.
FIG. 1A illustrates an example of a prior art solid blunt 103 within the shaft 105 of the needle assembly 101. The needle 107 includes a hollow opening 109 and a sharp tip 107 at the end of the opening. The needle assembly 101 is shown in FIG. 1A before its use. In this situation, the solid rod blunt 103 is disposed entirely within the shaft of the needle 105 such that the sharp point 107 can pierce an object, such as the skin of a patient. After use, the solid rod blunt 103 is advanced longitudinally along the longitudinal axis 120 shown in FIG. 1B such that the end 111 of the solid blunt 103 extends beyond the opening of the shaft 105, thereby to some extent covering the sharp tip 107 so that a user of the needle may not receive an accidental needle stick. As is well known in the art, a clip or other mechanism holds the solid blunt rod 103 relative to the shaft 105, preventing it from moving longitudinally along the axis 120 once the blunt 103 has been extended beyond the opening. However, as shown in FIG. 1C, it is also possible for the solid blunt 103 to move perpendicularly to the longitudinal axis 120 and this tends to increase the gap between the blunt and the sharp tip which tends to increase the likelihood of an accidental needle stick or skive. FIG. 1C shows a cross-sectional view of the assembly 101 shown in FIG. 1B at the line 1Cxe2x80x941C shown in FIG. 1B. As can be seen from FIG. 1C, there is a considerable gap 109a between the inner diameter of the shaft 105 and the outer diameter of the solid blunt rod 103. This makes it possible for the rod to move up and down along the axis 130 which is perpendicular to the longitudinal axis 120 shown in FIG. 1B. As a result, it is possible for the blunt 103 to be pushed away from the sharp tip 107 even when it is extended out beyond the tip 107 as shown in FIG. 1B. As a result, even though the blunt may be advanced longitudinally beyond the end of the sharp tip of the needle, the gap between the wall of the blunt and the sharp tip may be so large that the sharp point is permitted to scratch or skive a person""s skin. Naturally, the solid blunt must provide space around its circumference in order to permit fluid flow, and thus it would appear that a gap 109a is required.
From the above discussion, it can be seen that it is desirable to provide an improved solid blunt which better protects a user of a needle.
The present invention provides a solid blunt which helps to prevent accidental needle sticks. The present invention also provides a needle assembly having a solid blunt.
In one exemplary embodiment, a solid blunt has an outer dimension (e.g. outer diameter) which is nearly equal to an inner dimension (e.g. inner diameter) of a cannula of a needle which is configured to contain the solid blunt.
In one example, the solid blunt substantially blocks fluid flow along a first circumferential portion of an inner diameter of the cannula and allows fluid flow in a second circumferential portion of the inner diameter. The solid blunt is typically capable of longitudinal movement through the cannula and is prevented from moving substantially in a direction perpendicular to the longitudinal movement.
A needle assembly, in another exemplary embodiment, includes a solid blunt, a cannula, and a clip which couples the solid blunt to a frame which is coupled to the cannula. The clip allows the solid blunt to move longitudinally between at least two positions and the clip prevents the solid blunt from rotating within the shaft of the needle. The solid blunt itself is effectively lodged within the shaft of the needle so that it cannot move substantially in a direction perpendicular to the longitudinal movement of the solid blunt.
The present invention may be used with medical devices, including needles, catheter assemblies and introducers for catheters and other devices as well.